// Relationship detection engine
use crate::{
    CodeNode, EdgeType, NodeType, Result, SyntaxTree, SourceLocation,
};
use std::collections::HashMap;

/// Engine for detecting relationships between code elements
pub struct RelationshipDetectionEngine {
    /// Cache of detected relationships
    relationship_cache: HashMap<String, Vec<DetectedRelationship>>,
    /// Configuration for relationship detection
    config: RelationshipConfig,
}

/// Configuration for relationship detection
#[derive(Debug, Clone)]
pub struct RelationshipConfig {
    /// Whether to detect function calls
    pub detect_calls: bool,
    /// Whether to detect inheritance relationships
    pub detect_inheritance: bool,
    /// Whether to detect import relationships
    pub detect_imports: bool,
    /// Whether to detect variable references
    pub detect_references: bool,
    /// Whether to detect data flow relationships
    pub detect_data_flow: bool,
    /// Maximum depth for relationship traversal
    pub max_depth: u32,
}

impl Default for RelationshipConfig {
    fn default() -> Self {
        Self {
            detect_calls: true,
            detect_inheritance: true,
            detect_imports: true,
            detect_references: true,
            detect_data_flow: false, // More expensive, disabled by default
            max_depth: 10,
        }
    }
}

/// A detected relationship between code elements
#[derive(Debug, Clone)]
pub struct DetectedRelationship {
    pub source_name: String,
    pub target_name: String,
    pub relationship_type: EdgeType,
    pub confidence: f64,
    pub source_location: SourceLocation,
    pub target_location: Option<SourceLocation>,
    pub context: RelationshipContext,
}

/// Context information for a relationship
#[derive(Debug, Clone)]
pub struct RelationshipContext {
    pub description: String,
    pub metadata: HashMap<String, String>,
}

impl RelationshipDetectionEngine {
    pub fn new() -> Self {
        Self {
            relationship_cache: HashMap::new(),
            config: RelationshipConfig::default(),
        }
    }

    pub fn with_config(config: RelationshipConfig) -> Self {
        Self {
            relationship_cache: HashMap::new(),
            config,
        }
    }

    /// Detect all relationships in a syntax tree
    pub async fn detect_relationships(
        &mut self,
        tree: &dyn SyntaxTree,
        nodes: &[&dyn CodeNode],
    ) -> Result<Vec<DetectedRelationship>> {
        let mut relationships = Vec::new();

        // Create lookup maps for efficient searching
        let node_by_name = self.create_node_lookup(nodes);
        let _node_by_location = self.create_location_lookup(nodes);

        // Detect different types of relationships
        if self.config.detect_calls {
            let call_relationships = self.detect_function_calls(tree, &node_by_name).await?;
            relationships.extend(call_relationships);
        }

        if self.config.detect_inheritance {
            let inheritance_relationships = self.detect_inheritance(tree, &node_by_name).await?;
            relationships.extend(inheritance_relationships);
        }

        if self.config.detect_imports {
            let import_relationships = self.detect_imports(tree, &node_by_name).await?;
            relationships.extend(import_relationships);
        }

        if self.config.detect_references {
            let reference_relationships = self.detect_references(tree, &node_by_name).await?;
            relationships.extend(reference_relationships);
        }

        if self.config.detect_data_flow {
            let data_flow_relationships = self.detect_data_flow(tree, &node_by_name).await?;
            relationships.extend(data_flow_relationships);
        }

        // Cache the results
        let cache_key = format!("{}_{}", tree.language(), tree.source().len());
        self.relationship_cache.insert(cache_key, relationships.clone());

        Ok(relationships)
    }

    /// Create a lookup map from node names to nodes
    fn create_node_lookup<'a>(
        &self,
        nodes: &'a [&'a dyn CodeNode],
    ) -> HashMap<String, &'a dyn CodeNode> {
        nodes
            .iter()
            .map(|node| (node.name().to_string(), *node))
            .collect()
    }

    /// Create a lookup map from locations to nodes
    fn create_location_lookup<'a>(
        &self,
        nodes: &'a [&'a dyn CodeNode],
    ) -> HashMap<String, &'a dyn CodeNode> {
        nodes
            .iter()
            .map(|node| {
                let location_key = format!(
                    "{}:{}:{}",
                    node.location().file_path,
                    node.location().start_line,
                    node.location().start_column
                );
                (location_key, *node)
            })
            .collect()
    }

    /// Detect function call relationships
    async fn detect_function_calls(
        &self,
        tree: &dyn SyntaxTree,
        node_by_name: &HashMap<String, &dyn CodeNode>,
    ) -> Result<Vec<DetectedRelationship>> {
        let mut relationships = Vec::new();
        let source = tree.source();

        // Simple pattern matching for function calls
        // In a real implementation, we'd use Tree-sitter queries
        for (caller_name, caller_node) in node_by_name {
            if caller_node.node_type() == &NodeType::Function {
                // Look for function calls in the source code
                for (callee_name, callee_node) in node_by_name {
                    if callee_node.node_type() == &NodeType::Function && caller_name != callee_name {
                        let call_pattern = format!("{}(", callee_name);
                        if source.contains(&call_pattern) {
                            relationships.push(DetectedRelationship {
                                source_name: caller_name.clone(),
                                target_name: callee_name.clone(),
                                relationship_type: EdgeType::Calls,
                                confidence: 0.8,
                                source_location: caller_node.location().clone(),
                                target_location: Some(callee_node.location().clone()),
                                context: RelationshipContext {
                                    description: format!("{} calls {}", caller_name, callee_name),
                                    metadata: HashMap::new(),
                                },
                            });
                        }
                    }
                }
            }
        }

        Ok(relationships)
    }

    /// Detect inheritance relationships
    async fn detect_inheritance(
        &self,
        tree: &dyn SyntaxTree,
        node_by_name: &HashMap<String, &dyn CodeNode>,
    ) -> Result<Vec<DetectedRelationship>> {
        let mut relationships = Vec::new();
        let source = tree.source();

        // Look for class inheritance patterns
        for (child_name, child_node) in node_by_name {
            if child_node.node_type() == &NodeType::Class {
                for (parent_name, parent_node) in node_by_name {
                    if parent_node.node_type() == &NodeType::Class && child_name != parent_name {
                        // Look for inheritance patterns like "class Child(Parent):"
                        let inheritance_pattern = format!("class {}({})", child_name, parent_name);
                        if source.contains(&inheritance_pattern) {
                            relationships.push(DetectedRelationship {
                                source_name: child_name.clone(),
                                target_name: parent_name.clone(),
                                relationship_type: EdgeType::Inherits,
                                confidence: 0.9,
                                source_location: child_node.location().clone(),
                                target_location: Some(parent_node.location().clone()),
                                context: RelationshipContext {
                                    description: format!("{} inherits from {}", child_name, parent_name),
                                    metadata: HashMap::new(),
                                },
                            });
                        }
                    }
                }
            }
        }

        Ok(relationships)
    }

    /// Detect import relationships
    async fn detect_imports(
        &self,
        tree: &dyn SyntaxTree,
        node_by_name: &HashMap<String, &dyn CodeNode>,
    ) -> Result<Vec<DetectedRelationship>> {
        let mut relationships = Vec::new();
        let source = tree.source();

        // Look for import statements
        for (importer_name, importer_node) in node_by_name {
            for (imported_name, imported_node) in node_by_name {
                if importer_name != imported_name {
                    // Look for various import patterns
                    let import_patterns = vec![
                        format!("import {}", imported_name),
                        format!("from {} import", imported_name),
                        format!("from . import {}", imported_name),
                    ];

                    for pattern in import_patterns {
                        if source.contains(&pattern) {
                            relationships.push(DetectedRelationship {
                                source_name: importer_name.clone(),
                                target_name: imported_name.clone(),
                                relationship_type: EdgeType::Imports,
                                confidence: 0.95,
                                source_location: importer_node.location().clone(),
                                target_location: Some(imported_node.location().clone()),
                                context: RelationshipContext {
                                    description: format!("{} imports {}", importer_name, imported_name),
                                    metadata: HashMap::new(),
                                },
                            });
                            break;
                        }
                    }
                }
            }
        }

        Ok(relationships)
    }

    /// Detect variable reference relationships
    async fn detect_references(
        &self,
        tree: &dyn SyntaxTree,
        node_by_name: &HashMap<String, &dyn CodeNode>,
    ) -> Result<Vec<DetectedRelationship>> {
        let mut relationships = Vec::new();
        let source = tree.source();

        // Look for variable references
        for (referencer_name, referencer_node) in node_by_name {
            for (referenced_name, referenced_node) in node_by_name {
                if referencer_name != referenced_name {
                    // Simple pattern: variable name appears in the source
                    if source.contains(referenced_name) {
                        relationships.push(DetectedRelationship {
                            source_name: referencer_name.clone(),
                            target_name: referenced_name.clone(),
                            relationship_type: EdgeType::References,
                            confidence: 0.6, // Lower confidence for simple text matching
                            source_location: referencer_node.location().clone(),
                            target_location: Some(referenced_node.location().clone()),
                            context: RelationshipContext {
                                description: format!("{} references {}", referencer_name, referenced_name),
                                metadata: HashMap::new(),
                            },
                        });
                    }
                }
            }
        }

        Ok(relationships)
    }

    /// Detect data flow relationships (more complex analysis)
    async fn detect_data_flow(
        &self,
        _tree: &dyn SyntaxTree,
        _node_by_name: &HashMap<String, &dyn CodeNode>,
    ) -> Result<Vec<DetectedRelationship>> {
        // TODO: Implement data flow analysis
        // This would involve tracking variable assignments, function parameters,
        // return values, and how data flows through the program
        Ok(Vec::new())
    }

    /// Get cached relationships for a tree
    pub fn get_cached_relationships(&self, tree: &dyn SyntaxTree) -> Option<&Vec<DetectedRelationship>> {
        let cache_key = format!("{}_{}", tree.language(), tree.source().len());
        self.relationship_cache.get(&cache_key)
    }

    /// Clear the relationship cache
    pub fn clear_cache(&mut self) {
        self.relationship_cache.clear();
    }

    /// Get statistics about detected relationships
    pub fn get_relationship_stats(&self) -> RelationshipStats {
        let mut stats = RelationshipStats::default();

        for relationships in self.relationship_cache.values() {
            stats.total_relationships += relationships.len();
            
            for rel in relationships {
                match rel.relationship_type {
                    EdgeType::Calls => stats.call_relationships += 1,
                    EdgeType::Inherits => stats.inheritance_relationships += 1,
                    EdgeType::Imports => stats.import_relationships += 1,
                    EdgeType::References => stats.reference_relationships += 1,
                    EdgeType::DataFlow => stats.data_flow_relationships += 1,
                    _ => stats.other_relationships += 1,
                }
            }
        }

        stats
    }
}

impl Default for RelationshipDetectionEngine {
    fn default() -> Self {
        Self::new()
    }
}

/// Statistics about detected relationships
#[derive(Debug, Default)]
pub struct RelationshipStats {
    pub total_relationships: usize,
    pub call_relationships: usize,
    pub inheritance_relationships: usize,
    pub import_relationships: usize,
    pub reference_relationships: usize,
    pub data_flow_relationships: usize,
    pub other_relationships: usize,
}
